英语四级语法精讲——状语从句(6)

大学英语四级考试涉及的语法知识点多、涉及面宽，对不少考生来说都是一个难题。希望通过本专题的学习，考生能对四级语法有更全面的掌握！

6. 条件状语从句：

连接词：if, once, as long as, on condition that

① 如果引导的条件可以实现，主将从现；

② 如果引导的条件和事实相反，则用虚拟语气；

eg：If winter comes can spring be far behind.

As long as it doesn't rain, we can play.

You can go out on condition that you wear an overcoat.

Modern cars are far tougher to steal, as their engine management computer won't allow them to start unless they receive a unique ID code beamed out by the ignition (点火) key.